GWAS of Alcoholism Risk
What is Alcoholism? Alcoholism is a progressive disease that can affect people in many different ways. Such examples are: not being able to control your drinking habits, becoming dependent on alcohol, and having withdrawal symptoms from alcohol if not ingested regularly. This disease is very complex because this is not like another disease where one specific phenotype means you have this disease. This is progressive, meaning this is a spectrum disease and multiple phenotypes can occur. Because of this, alcoholism is influenced by many different factors. Genetics do play into this as well as psychological state, environment, and social pressures. This makes it a hard disease to study, but for this genome wide association test, they looked at the genetic component between twin siblings. A Quantitative-Trait Genome-Wide Association Study (GWAS) of Alcoholism This study mainly focused on the use of alcohol and its dependance. Methods and Results: The researchers conducted diagnostic interviews and took blood samples from Australian twin siblings or 8754 individuals (with 2602 alcohol dependents). A GWAS was performed of many different single nucleotide polymorphisms or SNPs selected for "informativeness for alcohol use disorder and associated quantitative traits". They also did family based association tests too, to see if this was passed on from children to offspring. Note: The diagnostic test was based around the assumption that in Australia, a standard drink 10 grams of alcohol or 0.01 liters. This test asked the subjects about their alcohol consumption (frequency of drinks a day, frequency of heavy drinking, frequency of drinking to intoxication, etc.). They were also asked about their smoking history or if they struggled with anxiety or depression because these feed into alcoholism. Many different SNPs were looked at in this study, but the researchers did not find one specific gene that caused alcoholism. In Figure 1, it shows that some of the SNPs that were not found to be genetically linked to each other. One can determine genetic linkage through the LOD score or Logarithm of Odds. The LOD score compares the likelihood of these genes being linked together to the chance of seeing this happen by random chance. If the LOD score is higher than 3.0, this means that the genes you have selected are genetically linked to each other. Genetic linkage occurs when the loci are physically close to each other on the chromosome and usually will not separate when going through meiosis. This means that these genes will be passed down together from the parental generation to the offspring. The researchers also noted that even though they did not find a specific gene linked to alcoholism, there are many other environmental factors as well that contribute to this disease. Overall, there are multiple SNPs and different environmental factors that contribute to one's susceptibility to alcoholism. References Genome-wide Association studies, Wikipedia, Retrieved Nov. 2014. Genetic Linkage, Wikipedia, Retrieved Nov. 2014. Alcoholism, Mayo Clinic, Aug. 9, 2012. Retrieved Nov. 2014. "A quantitative-trait genome wide association study of alcoholism risk in the community: findings and implications", Heath AC, Biol Psychiatry. 2011 Sep 15;70(6):513-8. doi: 10.1016/j.biopsych.2011.02.028. Epub 2011 May 6. PMID: 21529783.